1. Field of the Invention
This invention relates to a mounting head for an electronic component-mounting apparatus that picks up electronic components by vacuum and mounts the electronic components on a circuit board.
2. Prior Art
Conventionally, a mounting head for an electronic component-mounting apparatus of this kind has been proposed in Japanese Laid-Open Patent Publication (Kokai) No. 5-226884, which includes a nozzle holder having a plurality of vacuum nozzles mounted thereon in a manner capable of projecting and retracting vertically, and a holder support member secured to a bracket mounted on a main unit of the electronic component-mounting apparatus, for rotatably supporting the nozzle holder via a pair of upper and lower bearings. The nozzle holder has a hook support member mounted at an upper portion thereof. The hook support member has a plurality of engaging hooks corresponding to the vacuum nozzles, respectively, and extending perpendicularly downward therefrom in a pivotally movable manner. Further, the hook support member has an upper end surface thereof formed with an engaging groove for engagement with an output end of a rotation drive mechanism arranged in the main unit. That is, the output end of the rotation drive mechanism engages with the engaging groove to drive the nozzle holder for rotation, whereby one of the vacuum nozzles selected for use is brought to a projecting position.
Each of the vacuum nozzles has a hook-catching member fixed to an upper portion thereof for engagement with a corresponding one of the engaging hooks. Retraction of the vacuum nozzles into the nozzle holder is effected by lowering the mounting head and causing the vacuum nozzles to strike against a nozzle stopper, while downward projection of a selected vacuum nozzle from the nozzle holder is effected by pivotally moving a corresponding one of the engaging hooks by a disengaging mechanism provided in the main unit, to disengage the engaging hook from a corresponding one of the hook-catching members. That is, in changing (switching) vacuum nozzles in use, the nozzle holder is rotated to bring a vacuum nozzle selected for use in a next mounting operation to a projecting position, then all the vacuum nozzles are struck against the nozzle stopper to be once retracted into the nozzle holder, and thereafter, only the selected vacuum nozzle is caused to project.
As described above, in the conventional mounting head, all the vacuum nozzles are required to be struck against the stopper before causing one of the vacuum nozzles to project for use. Since this operation is repeatedly carried out, the striking end of each vacuum nozzle is worn away or deformed, which inevitably shortens the service life of the vacuum nozzle.